block: Initial support for data-less (or empty) barrier support
This implements functionality to pass down or insert a barrier
in a queue, without having data attached to it. The ->prepare_flush_fn()
infrastructure from data barriers are reused to provide this
functionality.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/mm/bounce.c b/mm/bounce.c
index 3b549bf..b6d2d0f 100644
--- a/mm/bounce.c
+++ b/mm/bounce.c
@@ -265,6 +265,12 @@
mempool_t *pool;
/*
+ * Data-less bio, nothing to bounce
+ */
+ if (bio_empty_barrier(*bio_orig))
+ return;
+
+ /*
* for non-isa bounce case, just check if the bounce pfn is equal
* to or bigger than the highest pfn in the system -- in that case,
* don't waste time iterating over bio segments